"Signage has been tried with mixed results," he says. "It appeared that this was, in part, due to the fact people didn't know what it was about."

To lift awareness of labelling, Caterson and his team designed an educational campaign to support the roll-out of mandatory menu board labelling.

Ahead of the launch however, Caterson and colleagues held a "baseline study" to survey consumer awareness of kilojoules and how this impacted on food choices.

Caterson says because the major focus of the campaign was 18 to 24-year-olds, social media was a key part of the campaign, known as 8700, which refers to the average Australian's daily intake of kilojoules.

Alongside traditional advertising, the education campaign used Facebook and search engine advertising, a website and a smartphone app.

After the campaign, two waves of feedback were held in which consumers were asked to complete an online survey or questioned in the food outlets.

The in-store interviews also asked people what they just purchased and converted their meal into kilojoules to measure the impact of the labelling regime and supporting campaign on knowledge and kilojoules purchased.

At each wave, 500 people were interviewed online and 800 in-store.

The researchers found improved awareness eight months after introduction of the legislation with a 14 per cent increase in the number of consumers able to nominate the correct range of the average daily energy intake (8000 to 8999 kilojoules).

Those who noticed the information in outlets increased from 15 per cent at the baseline study to 36 per cent.

Importantly, says Caterson, the amount of kilojoules per purchase was reduced by 519 kilojoules.

"Four hundred and eighteen kilojoules a day is a two kilogram weight loss in a year," says Caterson.

"This actually shows a change due to the campaign. The challenge is to sustain the effort and bring about a long-term commitment to behaviour change."

Mandatory food labelling in NSW was extended in March to include ready-made meals sold in supermarkets.